Curable composition for coatings

ABSTRACT

A curable coating composition is described comprising 
     (A) a carbamate- or urea-functional compound that is the reaction product of a mixture comprising 
     (1) a compound comprising a carbamate or urea group or a group that can be converted to carbamate or urea, and a hydroxyl functional group 
     (2) a compound comprising inorganic functional groups that are reactive with hydroxyl groups on a plurality of molecules of compound (A)(1), but that are not reactive with the carbamate or urea groups on compound (A)(1), 
     (B) a compound comprising a plurality of groups that are reactive with carbamate or urea.

This is a continuation of application Ser. No. 08/540,278, filed Oct. 6,1995 now abandoned.

FIELD OF THE INVENTION

This invention relates to curable coating compositions, particularly tocurable compositions utilizing a carbamate- or urea-functional compoundas one of the components of the composition.

BACKGROUND OF THE INVENTION

Curable coating compositions such as thermoset coatings are widely usedin the coatings art. They are often used for topcoats in the automotiveand industrial coatings industry. Color-plus-clear composite coatingsare particularly useful as topcoats where exceptional gloss, depth ofcolor, distinctness of image, or special metallic effects are desired.The automotive industry has made extensive use of these coatings forautomotive body panels. Color-plus-clear composite coatings, however,require an extremely high degree of clarity in the clearcoat to achievethe desired visual effect. High-gloss coatings also require a low degreeof visual aberations at the surface of the coating in order to achievethe desired visual effect such as high distinctness of image (DOI).

Such coatings are especially susceptible to a phenomenon known asenvironmental etch. Environmental etch manifests itself as spots ormarks on or in the finish of the coating that often cannot be rubbedout.

Curable coating compositions based on curable components havingcarbamate or urea functionality have been proposed have been describedin the art to provide etch-resistant coatings, e.g., U.S. Pat. No.5,356,669 and WO 94/10211.

In addition to resistance to environmental etch, a number of othercharacteristics can be desireable. For example, it may be desireable toprovide a coating having a high degree of flexibility. This can beparticularly advantageous if the substrate on which the coating isplaced is itself flexible, as in the case of plastic, leather, ortextile substrates.

It is also desirable to reduce the amount of solvent required in coatingcompositions in order to reduce the volatile organic content (VOC),which is better for the environment.

Finally, it is desirable to provide a variety of carbamate- orurea-functional to provide coatings with a good combination ofproperties such as durability, hardness, and resistance to scratching,marring, solvents, and acids.

SUMMARY OF THE INVENTION

According to the present invention, there is provided a coatingcomposition comprising

(A) a carbamate- or urea-functional compound that is the reactionproduct of a mixture comprising

(1) a compound comprising a carbamate or urea group or a group that canbe converted to carbamate or urea, and a hydroxyl functional group

(2) a compound comprising inorganic functional groups that are reactivewith hydroxyl groups on a plurality of molecules of compound (A) (1),but that are not reactive with the carbamate or urea groups on compound(A) (1),

(B) a curing agent comprising a plurality of groups that are reactivewith the functional groups on compound (A).

The present invention provides coatings having a good combination ofproperties such as durability, hardness, and resistance to scratching,marring, solvents, and acids. Coating compositions according to theinvention can also provide low VOC levels, and can be used to preparecoatings having good flexibility for use over flexible substrates.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

According to the present invention, compound (A) (1) has a carbamate orurea group (or a group that can be converted to carbamate or urea) and ahydroxyl group is reacted with a compound (A) (2) comprising inorganicfunctional groups that are reactive with hydroxyl groups on a pluralityof molecules of compound (A) (1), but that are not reactive with thecarbamate or urea groups on compound (A) (1). Reaction of just (A) (1)with (A) (2) will result in a compound having the residues of two (A)(1) compounds linked together by a the residue of compound (A) (2).Inclusion of a polyol in the reaction mixture, with appropriateadjustment of the amount of (A) (2) can result in an extended compound,as is known in the art, terminated with (A) (1) compounds. Useful diolsinclude 1,6-hexane diol, 2-ethyl-1,3-hexane diol, neopentyl glycol,cyclohexane-1,4-dimethylol, bisphenol A, polyether polyols such asPluronic® polyols sold by BASF Corporation, 1,2-hexane diol, and thelike. Useful polyols of higher functionality include trimethylolpropane, pentaerythritol, acrylic polyols, and the like. Also useful arediols having a pendant carbamate group or a pendant urea group. Diolshaving a pendant carbamate group can be formed by ring-opening ahydroxyalkyl-substituted cyclic carbonate with ammonia or a primaryamine using known techniques. Diols having a pendant carbamate group canbe formed by ring-opening a hydroxyalkyl-substituted oxazolidone withammonia or a primary amine using known techniques.

A number of compounds may be used as the compound (A) (1) having acarbamate or urea group (or group that can be converted to carbamate orurea) and a hydroxyl group.

Carbamate groups can generally be characterized by the formula ##STR1##wherein R is H or alkyl, preferably of 1 to 4 carbon atoms. Preferably,R is H or methyl, and more preferably R is H. Urea groups can generallybe characterized by the formula ##STR2## wherein R' and R" eachindependently represents H or alkyl, preferably of 1 to 4 carbon atoms,or R' and R" may together form a heterocyclic ring structure (e.g.,where R' and R" form an ethylene bridge).

Compounds having a carbamate or urea group (or group that can beconverted to carbamate or urea) and a hydroxyl group are known in theart and are commercially available. These include, for example,hydroxyalkyl carbamates (e.g., hydroxypropyl carbamate, hydroxybutylcarbamate), hydroxy ureas (e.g., hydroxyethyl ethylene urea), andhydroxyalkyl cyclic carbonates, which can be converted to carbamate byring-opening the cyclic carbonate with ammonia or a primary amine asdescribed below.

Another group of compounds having a carbamate or urea group (or groupthat can be converted to carbamate or urea) and a hydroxyl group arecompounds formed by reacting a lactone or a hydroxy carboxylic acid witha compound having an active hydrogen group capable of ring-opening thelactone (e.g., hydroxyl, primary amine, acid) or capable of undergoing acondensation reaction with the acid group of the hydroxy carboxylicacid, and a carbamate or urea group or a group that can be converted tocarbamate or urea. When a compound having an active hydrogen group and agroup that can be converted to carbamate or urea is used to ring-openthe lactone, conversion of the group to a carbamate or urea can beaccomplished during or after the ring-opening reaction.

Compounds having a carbamate or urea group and an active hydrogen groupare known in the art. Hydroxypropyl carbamate and hydroxyethyl ethyleneurea, for example, are well known and commercially available. Aminocarbamates are described in U.S. Pat. No. 2,842,523. Hydroxyl ureas mayalso be prepared by reacting an oxazolidone with ammonia or a primaryamine or by reacting ethylene oxide with ammonia to form an aminoalcohol and then reacting the amine group of that compound or any otheramino alcohol with hydrochloric acid, then urea to form a hydroxy urea.Amino ureas can be prepared, for example, by reacting a ketone with adiamine having one amine group protected from reaction (e.g., by sterichindrance), followed by reaction with HNCO (i.e., the product of thethermal decomposition of urea), and then water. Alternatively, thesecompounds can be prepared by starting with a compound having an activehydrogen and a group that can be converted to carbamate or urea asdescribed below, and then converting that group to the carbamate or ureaprior to commencement of the lactone ring-opening reaction.

Groups that can be converted to carbamate include cyclic carbonategroups, epoxy groups, and unsaturated bonds. Cyclic carbonate groups canbe converted to carbamate groups by reaction with ammonia or a primaryamine, which ring-opens the cyclic carbonate to form a β-hydroxycarbamate. Epoxy groups can be converted to carbamate groups by firstconverting to a cyclic carbonate group by reaction with CO₂. This can bedone at any pressure from atmospheric up to supercritical CO₂ pressures,but is preferably under elevated pressure (e.g., 60-150 psi). Thetemperature for this reaction is preferably 60°-150° C. Useful catalystsinclude any that activate an oxirane ring, such as tertiary amine orquaternary salts (e.g., tetramethyl ammonium bromide), combinations ofcomplex organotin halides and alkyl phosphonium halides (e.g., (CH₃)₃SnI, Bu₄ SnI, Bu₄ PI, and (CH₃)₄ PI), potassium salts (e.g., K₂ CO₃, KI)preferably in combination with crown ethers, tin octoate, calciumoctoate, and the like. The cyclic carbonate group can then be convertedto a carbamate group as described above. Any unsaturated bond can beconverted to carbamate groups by first reacting with peroxide to convertto an epoxy group, then with CO₂ to form a cyclic carbonate, and thenwith ammonia or a primary amine to form the carbamate.

Other groups, such as hydroxyl groups or isocyanate groups can also beconverted to carbamate groups. However, if such groups were to bepresent on the compound and then converted to carbamate after thering-opening reaction with the lactone, they would have to be blocked sothat they would not react with the lactone or with the active hydrogengroups involved in the lactone ring-opening reaction. When blockingthese groups is not feasible, the conversion to carbamate or urea wouldhave to be completed prior to the lactone ring-opening reaction.Hydroxyl groups can be converted to carbamate groups by reaction with amonoisocyanate (e.g., methyl isocyanate) to form a secondary carbamategroup or with cyanic acid (which may be formed in situ by thermaldecomposition of urea) to form a primary carbamate group (i.e.,unsubstituted carbamates). This reaction preferably occurs in thepresence of a catalyst as is known in the art. A hydroxyl group can alsobe reacted with phosgene and then ammonia to form a compound havingprimary carbamate group(s), or by reaction of a hydroxyl with phosgeneand then a primary amine to form a compound having secondary carbamategroups. Another approach is to react an isocyanate with a compound suchas hydroxyalkyl carbamate to form a carbamate-capped isocyanatederivative. For example, one isocyanate group on toluene diisocyanatecan be reacted with hydroxypropyl carbamate, followed by reaction of theother isocyanate group with an excess of polyol to form a hydroxycarbamate. Finally, carbamates can be prepared by a transesterificationapproach where hydroxyl group reacted with an alkyl carbamate (e.g.,methyl carbamate, ethyl carbamate, butyl carbamate) to form a primarycarbamate group-containing compound. This reaction is performed underheat, preferably in the presence of a catalyst such as an organometalliccatalyst (e.g., dibutyltin dilaurate). Other techniques for preparingcarbamates are also known in the art and are described, for example, inP. Adams & F. Baron, "Esters of Carbamic Acid", Chemical Review, v. 65,1965.

Groups such as oxazolidone can also be converted to urea after thering-opening reaction with the lactone. For example, hydroxyethyloxazolidone can be used to initiate the ring-opening reaction with thelactone, followed by reaction of ammonia or a primary amine with theoxazolidone to generate the urea functional group.

Other groups, such as amino groups or isocyanate groups can also beconverted to urea groups. However, if such groups were to be present onthe compound and then converted to urea after the ring-opening reactionwith the lactone, they would have to be blocked so that they would notreact with the lactone or with the active hydrogen groups involved inthe lactone ring-opening reaction. When blocking these groups is notfeasible, the conversion to carbamate or urea would have to be completedprior to the lactone ring-opening reaction. Amino groups can beconverted to urea groups by reaction with a monoisocyanate (e.g., methylisocyanate) to form a secondary urea group or with cyanic acid (whichmay be formed in situ by thermal decomposition of urea) to form aprimary urea group. This reaction preferably occurs in the presence of acatalyst as is known in the art. An amino group can also be reacted withphosgene and then ammonia to form a compound having primary ureagroup(s), or by reaction of an amino group with phosgene and then aprimary amine to form a compound having secondary urea groups. Anotherapproach is to react an isocyanate with a hydroxy urea compound to forma urea-capped isocyanate derivative. For example, one isocyanate groupon toluene diisocyanate can be reacted with hydroxyethyl ethylene urea,followed by reaction of the other isocyanate group with an excess ofpolyol to form a hydroxy carbamate.

One preferred class of compounds having an active hydrogen group and agroup that can be converted to carbamate is the hydroxyalkyl cycliccarbonates. Hydroxyalkyl cyclic carbonates can be prepared by a numberof approaches. Certain hydroxyalkyl cyclic carbonates like3-hydroxypropyl carbonate (i.e., glycerine carbonate) are commerciallyavailable. Cyclic carbonate compounds can be synthesized by any ofseveral different approaches. One approach involves reacting an epoxygroup-containing compound with CO₂ under conditions and with catalystsas described hereinabove. Epoxides can also be reacted withβ-butyrolactone in the presence of such catalysts. In another approach,a glycol like glycerine is reacted at temperatures of at least 80° C.with diethyl carbonate in the presence of a catalyst (e.g., potassiumcarbonate) to form a hydroxyalkyl carbonate. Alternatively, a functionalcompound containing a ketal of a 1,2-diol having the structure: ##STR3##can be ring-opened with water, preferably with a trace amount of acid,to form a 1,2-glycol, which is then further reacted with diethylcarbonate to form the cyclic carbonate.

Cyclic carbonates typically have 5-6-membered rings, as is known in theart. Five-membered rings are preferred, due to their ease of synthesisand greater degree of commercial availability. Six-membered rings can besynthesized by reacting phosgene with 1,3-propane diol under conditionsknown in the art for the formation of cyclic carbonates. Preferredhydroxyalkyl cyclic carbonates used in the practice can be representedby the formula: ##STR4## where R (or each instance of R if n is morethan 1) is a hydroxyalkyl group of 1-18 carbon atoms, preferably 1-6carbon atoms, and more preferably 1-3 carbon atoms, which may be linearor branched and may have subsituents in addition to the hydroxyl (whichitself may be primary, secondary, or tertiary), and n is 1 or 2, whichmay be substituted by one or more other substituents such as blockedamines or unsaturated groups. More preferably, R is --C_(m) H^(2m) OHwhere the hydroxyl may be primary or secondary and m is 1 to 8, and evenmore preferably, R is --(CH₂)_(p) --OH where the hydroxyl is primary andp is 1 to 2.

Lactones that can be ring opened by an active hydrogen are well-known inthe art. They include, for example, ε-caprolactone, γ-caprolactone,β-butyrolactone, β-propriolactone, γ-butyrolactone,α-methyl-γ-butyrolactone, β-methyl-γ-butyrolactone, γ-valerolactone,δ-valerolactone, γ-nonanoic lactone, γ-octanoic lactone, andpentolactone. In one preferred embodiment, the lactone isε-caprolactone. Lactones useful in the practice of the invention canalso be characterized by the formula: ##STR5## wherein n is a positiveinteger of 1 to 7 and R is one or more H atoms, or substituted orunsubstituted alkyl groups of 1-7 carbon atoms.

The lactone ring-opening reaction is typically conducted under elevatedtemperature (e.g., 80°-150° C.). The reactants are usually liquids so asolvent is not necessary. However, a solvent may be useful in promotinggood conditions for the reaction even if the reactants are liquid. Anynon-reactive solvent may be used, including both polar and nonpolarorganic solvents. Examples of useful solvents include toluene, xylene,methyl ethyl ketone, methyl isobutyl ketone, and the like. A catalyst ispreferably present. Useful catalysts include proton acids (e.g.,octanoic acid, Amberlyst® 15 (Rohm & Haas)), and tin catalysts (e.g.,stannous octoate). Alternatively, the reaction can be initiated byforming a sodium salt of the hydroxyl group on the molecules to reactwith the lactone ring.

The lactone ring-opening reaction provides chain extension of themolecule if sufficient amounts of the lactone are present. The relativeamounts of the carbamate or urea compound and the lactone can be variedto control the degree of chain extension. The opening of the lactonering with a hydroxyl or amine group results in the formation of an esteror amide and an OH group. The OH group can then react with anotheravailable lactone ring, thus resulting in chain extension. The reactionis thus controlled by the proportion of lactone in the relative to theamount of the active hydrogen initiator compound. In the practice of thepresent invention, the ratio of equivalents of lactone to equivalents ofactive hydrogen groups is preferably from 0.1:1 to 10:1, and morepreferably from 1:1 to 5:1. When the lactone is opened with with anacid, the resulting compound has an acid group, which can then beconverted to a hydroxyl group by well-known techniques such as reactionwith ethylene oxide.

A compound (A) (1) having a hydroxyl active hydrogen group can also bereacted with a hydroxy carboxylic acid to form the carbamate- orurea-functional compound (A). Useful hydroxy carboxylic acids includedimethylhydroxypropionic acid, hydroxy stearic acid, tartaric acid,lactic acid, 2-hydroxyethyl benzoic acid, and N-(2-hydroxyethyl)ethylenediamine triacetic acid. The reaction can be conducted under typicaltransesterification conditions, e.g., temperatures from room temperatureto 150° C. with transesterification catalysts such as such as calciumoctoate, metal hydroxides (e.g., KOH), Group I or II metals (e.g., Na,Li), metal carbonates (e.g., K₂ CO₃) which may be enhanced by use incombination with crown ethers, metal oxides (e.g., dibutyltin oxide),metal alkoxides (e.g., NaOCH₃, Al(OC₃ H₇)₃), metal esters (e.g.,stannous octoate, calcium octoate, or protic acids (e.g., H₂ SO₄),MgCO₃, or Ph₄ SbI. The reaction may also be conducted at roomtemperature with a polymer-supported catalyst such as Amberlyst-15®(Rohm & Haas) as described by R. Anand, Synthetic Communications,24(19), 2743-47 (1994), the disclosure of which is incorporated hereinby reference.

The reaction of compound (A) (1) with compound (A) (2) (and conversionof the group(s) that are convertible to carbamate or urea) will itselfresult in a compound having the residues of two (A) (1) compounds linkedtogether by a the residue of compound (A) (2). Inclusion of a polyol inthe reaction mixture, with appropriate adjustment of the amount of (A)(2) will result in an extended compound, as is known in the art,terminated with (A) (1) compounds. The of equivalents of (A) (1) to (A)(2) should be adjusted as is known in the art to achieve the desiredlevel of chain extension. Diols may be preferred as they provide linearchain extension, although polyols of higher functionality can be used ifbranching is desired. Virtually any diol or other polyol may be used,depending on the properties desired. Examples of useful polyols caninclude 1,6-hexane diol, 2-ethyl-1,3-hexane diol, neopentyl glycol,cyclohexane-1,4-dimethylol, bisphenol A, polyether polyols such asPluronic® polyols sold by BASF Corporation, 1,2-hexane diol, and thelike. Useful polyols of higher functionality include trimethylolpropane, pentaerythritol, acrylic polyols, and the like.

Compounds useful as (A) (2) include phosphorus compounds such as POCl₃or hexachlorocyclotriphosphazene, SO₂ sources such as SO₃ or SO₂ Cl₂, orsilane-based systems such as substituted or unsubstituted cyclicsiloxanes or silanes, or substituted or unsubstituted linear siloxanesor silanes, which may be described by the formula SiX_(m) R_(n) where Xis a group that is reactive with protons, such as a halide, alkoxy,hydride, or acetate, R is a group that is non-reactive with protons suchas alkyl, silane, or siloxane, m=2-4, and m+n=4.

Phosphazene or POCl₃ may be used as compound (A) (2) to react with (A)(1). In a typical reaction, one equivalent (based on chlorine content)of the phosphorus reagent is dissolved in a dry ether solvent such asdiethyl ether of tetrahydrofuran to form a solution of approximately50%. 1.5 equivalents of sodium hydride are added followed by oneequivalent of (A) (1) (or (A) (1) plus other hydroxy carbamate or ureacompounds). The mixture is allowed to exotherm to the reflux temperatureof the solvent, with the reaction temperature controlled by the additionrate of the (A) (1) compound. After addition of the (A) (1) compound iscomplete, the reaction mixture is heated to reflux and held for 2-3hours. The mixture is then cooled, filtered to remove sodium chlorideand any unreacted sodium hydride, and the solvent removed under vacuum.

Silane-based compounds may also be used as compound (A) (2). Suchcompounds may be described by the formula SiX_(m) R_(n) where X is agroup that is reactive with protons, such as a halide, alkoxy, hydride,or acetate, R is a group that is non-reactive with protons such asalkyl, silane, or siloxane, m=2-4, and m+n=4. These compounds may reactwith (A) (1) in any dry aprotic solvent (e.g., tetrahydrofuran) underconditions known in the art, which may depend on the nature of the Xgroup. When X is a hydride, the reaction is preferably begun withchilled reactants (e.g., 0° C.) under an inert atmosphere usingcatalysts such as tin catalysts. After the addition of materials iscomplete, amd dry methanol is added to react with any free remainingSi--H bonds. If X is a halide, the reaction is preferably begun under aninert atmosphere at room temperature. The mixture is then heated toreflux to drive the reaction to completion. HCl is given off as aby-product. If X is alkoxy, the reaction is preferably begun under aninert atmosphere at room temperature, which may be maintained for theduration of the reaction. A molecular sieve may be used to absorb thealcohol side product that is formed. Slightly basic or acidic pH willaccelerate this reaction; however, it will also accelerate the formationof Si--O--Si bonds.

For SO₂ sources, the SO₃ can be reacted with the (A) (1) by bubbling SO₃through the (A) (1) compound if it is in liquid form or by dissolving(A) (1) in a solvent and then bubbling SO₃ through the solution. Thereaction of SO₂ Cl₂ with (A) (1) may be assisted by the pre-reaction of(A) (1) with Na or NaOR (where R is an organic radical).

The composition of the invention is cured by a reaction of thecarbamate- or urea-functional compound (A) with a component (B) that isa compound having a plurality of functional groups that are reactivewith the carbamate or urea groups on component (A). Such reactive groupsinclude active methylol or methylalkoxy groups on aminoplastcrosslinking agents or on other compounds such as phenol/formaldehydeadducts, siloxane or silane groups, and anhydride groups. Examples of(B) compounds include melamine formaldehyde resin (including monomericor polymeric melamine resin and partially or fully alkylated melamineresin), urea resins (e.g., methylol ureas such as urea formaldehyderesin, alkoxy ureas such as butylated urea formaldehyde resin),N-methylol acrylamide emulsions, isobutoxy methyl acrylamide emulsions,polyanhydrides (e.g., polysuccinic anhydride), and siloxanes or silanes(e.g., dimethyldimethoxy silane). Aminoplast resin such as melamineformaldehyde resin or urea formaldehyde resin are especially preferred.Also preferred are aminoplast resins where one or more of the aminonitrogens is substituted with a carbamate group for use in a processwith a curing temperature below 150° C., as described in U.S. Pat. No.5,300,328.

A solvent may optionally be utilized in the coating composition used inthe practice of the present invention. The coating composition accordingto the present invention can be applied without solvent, especially ifthe degree of chain extension for component (A) is limited. However, inmany cases, it is desirable to use a solvent in the coating compositionas well. This solvent should act as a solvent with respect to both thecarbamate- or urea-functional compound (A) as well as the component (B).In general, depending on the solubility characteristics of components(A) and (B), the solvent can be any organic solvent and/or water. In onepreferred embodiment, the solvent is a polar organic solvent. Morepreferably, the solvent is a polar aliphatic solvents or polar aromaticsolvents. Still more preferably, the solvent is a ketone, ester,acetate, aprotic amide, aprotic sulfoxide, or aprotic amine. Examples ofuseful solvents include methyl ethyl ketone, methyl isobutyl ketone,amyl acetate, ethylene glycol butyl ether-acetate, propylene glycolmonomethyl ether acetate, xylene, N-methylpyrrolidone, or blends ofaromatic hydrocarbons. In another embodiment, the solvent can be wateror a mixture of water with co-solvents.

The coating composition used in the practice of the invention mayinclude a catalyst to enhance the cure reaction. For example, whenaminoplast compounds, especially monomeric melamines, are used ascomponent (B), a strong acid catalyst may be utilized to enhance thecure reaction. Such catalysts are well-known in the art and include, forexample, p-toluenesulfonic acid, dinonylnaphthalene disulfonic acid,dodecylbenzenesulfonic acid, phenyl acid phosphate, monobutyl maleate,butyl phosphate, and hydroxy phosphate ester. Other catalysts that maybe useful in the composition of the invention include Lewis acids, zincsalts, and tin salts.

Although a solvent may be present in the coating composition in anamount of from about 0.01 weight percent to about 99 weight percent, itis preferably present in an amount of less than 35%, more preferablyless than 25% and most preferably less than 15%. The coating compositionpreferably has a VOC (VOC is defined herein as VOC according to ASTMD3960) of less than 3.5 lbs/gal, more preferably less than 2.5 lbs/gal,and most preferably less than 1.5 lbs/gal.

Coating compositions can be coated on the article by any of a number oftechniques well-known in the art. These include, for example, spraycoating, dip coating, roll coating, curtain coating, and the like. Forautomotive body panels, spray coating is preferred. One advantage thatcan be achieved with coating compositions according to the invention isthat coatings with a high degree of flexibility can be prepared.Accordingly, in a preferred embodiment, the substrate onto which thecoating is applied is flexible, such as plastic, leather, or textilesubstrates.

Any additional agent used, for example, surfactants, fillers,stabilizers, wetting agents, dispersing agents, adhesion promoters, UVabsorbers, HALS, etc. may be incorporated into the coating composition.While the agents are well-known in the prior art, the amount used mustbe controlled to avoid adversely affecting the coating characteristics.

In one preferred embodiment, the coating composition according to theinvention is preferably utilized in a high-gloss coating and/or as theclearcoat of a composite color-plus-clear coating. High-gloss coatingsas used herein are coatings having a 20° gloss (ASTM D523-89) or a DOI(ASTM E430-91) of at least 80. In other preferred embodiments, thecoating composition may be utilized to prepare high-gloss or low-glossprimer or enamel coatings.

When the coating composition of the invention is used as a high-glosspigmented paint coating, the pigment may be any organic or inorganiccompounds or colored materials, fillers, metallic or other inorganicflake materials such as mica or aluminum flake, and other materials ofkind that the art normally names as pigments. Pigments are usually usedin the composition in an amount of 2% to 350%, based on the total weight(not including solvent) of components A and B (i.e., a P:B ratio of 0.02to 3.5).

When the coating composition according to the invention is used as theclearcoat of a composite color-plus-clear coating, the pigmentedbasecoat composition may any of a number of types well-known in the art,and does not require explanation in detail herein. Polymers known in theart to be useful in basecoat compositions include acrylics, vinyls,polyurethanes, polycarbonates, polyesters, alkyds, and siloxanes.Preferred polymers include acrylics and polyurethanes. In one preferredembodiment of the invention, the basecoat composition also utilizes acarbamate-functional acrylic polymer. Basecoat polymers are preferablycrosslinkable, and thus comprise one or more type of cross-linkablefunctional groups. Such groups include, for example, hydroxy,isocyanate, amine, epoxy, acrylate, vinyl, silane, and acetoacetategroups. These groups may be masked or blocked in such a way so that theyare unblocked and available for the cross-linking reaction under thedesired curing conditions, generally elevated temperatures. Usefulcross-linkable functional groups include hydroxy, epoxy, acid,anhydride, silane, and acetoacetate groups. Preferred cross-linkablefunctional groups include hydroxy functional groups and amino functionalgroups.

Basecoat polymers may be self-cross-linkable, or may require a separatecross-linking agent that is reactive with the functional groups of thepolymer. When the polymer comprises hydroxy functional groups, forexample, the cross-linking agent may be an aminoplast resin, isocyanateand blocked isocyanates (including isocyanurates), and acid or anhydridefunctional cross-linking agents.

The coating compositions described herein are preferably subjected toconditions so as to cure the coating layers. Although various methods ofcuring may be used, heat-curing is preferred. Generally, heat curing iseffected by exposing the coated article to elevated temperaturesprovided primarily by radiative heat sources. Curing temperatures willvary depending on the particular blocking groups used in thecross-linking agents, however they generally range between 93° C. and1770° C. The coating composition according to the present invention iscurable even at relatively low cure temperatures. Thus, in a preferredembodiment, the cure temperature is preferably between 115° C. and 150°C., and more preferably at temperatures between 115° C. and 138° C. fora blocked acid catalyzed system. For an unblocked acid catalyzed system,the cure temperature is preferably between 82° C. and 99° C. The curingtime will vary depending on the particular components used, and physicalparameters such as the thickness of the layers, however, typical curingtimes range from 15 to 60 minutes, and preferably 15-25 minutes forblocked acid catalyzed systems and 10-20 minutes for unblocked acidcatalyzed systems.

The invention is further described in the following examples.

Preparation 1

To 171.1 parts of dry amyl acetate was added 119 parts hydroxypropylcarbamate and 0.09 parts of stannous octoate. The system was heatedunder inert atmosphere to 60° C. 60 parts of X1-9623, a D4 cyclic MeHsiloxane from Dow Corning was added over 40 minutes. During the additionof siloxane, the temperature was allowed to go up to 70° C. Once all thesiloxane had been added, and hydrogen gas evolution had ceased, thereaction was held at 60° C. for one additional hour.

EXAMPLE 1

A paint mixture of 6.90 parts of the Preparation 1, 1.45 parts ofResimene® 747 (a methoxylated melamine from Monsanto), and 0.05 parts ofdodecyl benzene sulfonic acid was drawn down to 8 mm on a glasssubstrate. The coated substrate was cured at 270° F. for 30 minutes.

The resulting smooth film was smooth passed 200 methylethyl ketonedouble rubs with no noticeable effect to the film.

The invention has been described in detail with reference to preferredembodiments thereof. It should be understood, however, that variationsand modifications can be made within the spirit and scope of theinvention.

What is claimed is:
 1. A curable coating composition comprising(A) acompound comprising at least one functional group selected from thegroup consisting of carbamate groups, urea groups, and mixtures thereof,that is the reaction product of a mixture comprising:(1) a compoundcomprising a carbamate or urea group or a group that can be converted toa carbamate or urea group, and a hydroxyl functional group, (2) acompound comprising at least one functional group that contains an atomselected from the group consisting of phosphorous, sulfur, and silicon;wherein said functional group is reactive with hydroxyl groups on aplurality of molecules of compound (A) (1), but not reactive with thecarbamate or urea groups on compound (A) (1), wherein the carbamategroup has a formula ##STR6## wherein R is H or alkyl; and furtherwherein the urea group has a formula ##STR7## wherein R' and R" eachindependently are H or alkyl, or R' and R" together form a heterocyclicring structure; and (B) a curing agent comprising a plurality of groupsthat are reactive with the functional groups on compound (A).
 2. Acoating composition according to claim 1 wherein said compound (A) (1)is a hydroxyalkyl carbamate.
 3. A coating composition according to claim1 wherein said compound (A) (1) is a hydroxyalkyl-substituted cycliccarbonate.
 4. A coating composition according to claim 1 wherein saidcompound (A) (1) is the reaction product of(a) a compound comprising acarbamate or urea group or a group that can be converted to a carbamateor urea group, and a group having an active hydrogen selected from thegroup consisting of a hydroxyl, an amino, an acid, and mixtures thereof,and (b) a lactone.
 5. A coating composition according to claim 1 whereinsaid compound (A) (2) is selected from the group consisting of POCl₃,phosphazene, SO₂, cyclic siloxanes and silanes, linear siloxanes andsilanes, and mixtures thereof.
 6. A coating composition according toclaim 1 wherein said compound (A) is the reaction product of a mixturecomprising(1) a compound comprising at least one carbamate or urea groupor a group that can be converted to carbamate or urea, and at least onehydroxyl group, (2) a polyol, and (3) a compound comprising inorganicfunctional groups that are reactive with hydroxyl groups on a pluralityof molecules of compound (A) (1), but that are not reactive with thecarbamate or urea groups on compound (A) (1).
 7. A coating compositionaccording to claim 6 wherein said polyol includes a polyol compoundhaving at least one carbamate group attached thereto.
 8. A coatingcomposition according to claim 6 wherein said compound (1) is ahydroxyalkyl carbamate.
 9. A coating composition according to claim 6wherein said compound (1) is a hydroxyalkyl-substituted cycliccarbonate.
 10. A coating composition according to claim 6 wherein saidcompound (1) is the reaction product of(a) a compound comprising acarbamate or urea group or a group that can be converted to a carbamateor urea group, and a group having an active hydrogen selected from thegroup consisting of a hydroxyl, an amino, an acid, and mixtures thereof,and (b) a lactone.
 11. A coating composition according to claim 1wherein compound (B) is an aminoplast.
 12. A coating compositionaccording to claim 11 wherein said aminoplast is a melamine resin.
 13. Acoating composition according to claim 1 having a volatile organiccompound content of less than 3.5 lbs/gal.
 14. A coating compositionaccording to claim 1 having a volatile organic compound content of lessthan 2.5 lbs/gal.
 15. A coating composition according to claim 1 havinga volatile organic compound content of less than 1.5 lbs/gal.
 16. Acoating composition according to claim 1 that is a liquid and comprisesless than 35 weight percent of nonreactive organic solvent.
 17. Acoating composition according to claim 16 that is a liquid and comprisesless than 25 weight percent of nonreactive organic solvent.
 18. Acoating composition according to claim 16 that is a liquid and comprisesless than 15 weight percent of nonreactive organic solvent.
 19. Acoating composition according to claim 1 that is a clear coatingcomposition.
 20. A coating composition according to claim 1, furthercomprising a pigment.
 21. An article comprising a substrate havingthereon a cured coating derived from a coating composition according toclaim
 1. 22. An article according to claim 21 wherein said substrate isa flexible substrate.
 23. A cured coating, comprising the reactionproduct of:(A) a compound comprising at least one functional groupselected from the group consisting of carbamate groups, urea groups, andmixtures thereof, that is the reaction product of a mixturecomprising:(1) a compound comprising a carbamate or urea group or agroup that can be converted to a carbamate or urea group, and a hydroxylfunctional group, (2) a compound comprising at least one functionalgroup that contains an atom selected from the group consisting ofphosphorous, sulfur, and silicon; wherein said functional group isreactive with hydroxyl groups on a plurality of molecules of compound(A) (1), but not reactive with the carbamate or urea groups on compound(A) (1), wherein the carbamate group has a formula ##STR8## wherein R isH or alkyl; and further wherein the urea group has a formula ##STR9##wherein R' and R" each independently are H or alkyl, or R' and R"together form a heterocyclic ring structure; and (B) a curing agentcomprising a plurality of groups that are reactive with the functionalgroups on compound (A).
 24. A cured coating according to claim 23,wherein said compound (A) (1) is a hydroxyalkyl carbamate.
 25. A curedcoating according to claim 23, wherein said compound (A) (1) is ahydroxyalkyl-substituted cyclic carbonate.
 26. A coating compositionaccording to claim 23, wherein said compound (A) (1) is the reactionproduct of(a) a compound comprising a carbamate or urea group or a groupthat can be converted to a carbamate or urea group, and a group havingan active hydrogen selected from the group consisting of a hydroxyl, anamino, an acid, and mixtures thereof, and (b) a lactone.
 27. A curedcoating according to claim 23, wherein said compound (A) (2) is selectedfrom the group consisting of POCl₃, phosphazene, SO₂, cyclic siloxanesand silanes, linear siloxanes and silanes, and mixtures thereof.
 28. Acured coating according to claim 23, wherein said compound (A) is thereaction product of a mixture comprising, in addition to said compound(A) (1) and said compound (A) (2), a polyol.
 29. A cured coatingaccording to claim 28, wherein said polyol includes a polyol compoundhaving at least one carbamate group attached thereto.
 30. A curedcoating according to claim 28, wherein said compound (A) (1) is ahydroxyalkyl carbamate.
 31. A cured coating according to claim 28,wherein said compound (A) (1) is a hydroxyalkyl-substituted cycliccarbonate.
 32. A coating composition according to claim 28, wherein saidcompound (A) (1) is the reaction product of(a) a compound comprising acarbamate or urea group or a group that can be converted to a carbamateor urea group, and a group having an active hydrogen selected from thegroup consisting of a hydroxyl, an amino, an acid, and mixtures thereof,and (b) a lactone.
 33. A cured coating according to claim 23, whereincompound (B) is an aminoplast.
 34. A cured coating according to claim33, wherein said aminoplast is a melamine resin.
 35. A cured coatingaccording to claim 23 that is a clear coat.
 36. A cured coatingaccording to claim 23, further comprising a pigment.
 37. An articlecomprising a substrate having thereon a cured coating according to claim23.